The present invention relates generally to apparatus for weighing bulk material, and relates more specifically to a weighing apparatus for weighing bulk material transported by a conveyor belt.
The accurate weight measurement of bulk materials transported by belt-type conveyors is necessary for proper accounting and processing of the materials. Apparatus for weighing bulk materials on conveyor belts, known in the prior art, typically included a weighing section that was suspended from the conveyor system by four or more load cells. The weight of the material on the conveyor was continuously monitored by summing the force outputs of the load cells as the material was conveyed past the weighing section.
Several disadvantages inherent in prior art bulk material weighing apparatus have been encountered. One disadvantage was the excessive time that was required for the initial set-up and load calibration. A time-consuming adjustment process was necessary to evenly distribute the weight of the weighing section and the material carried thereby among all load cells. Because of the rigidity of the weighing section, a mis-adjusted load cell would carry a disproportionate share of the load thus reducing the weighing accuracy of the apparatus. Replacement of a malfunctioning load cell required that the time-comsuming adjustment process be repeated. Another related disadvantage was that the weighing accuracy of these prior art weighing apparatus was related to operating temperature. A change in the ambient temperature tended to dimensionally warp the welded weighing section. This warpage caused uneven loading of the load cells and a corresponding loss in weighing accuracy. The economic importance of eliminating such inaccuracies is substantial since the volume of material being weighed on belt-type conveyors is very substantial and even small errors will result in very sizeable cost differences.